These techniques which achieve pasteurisation at lower temperatures also provide for improvements in maturation processes during pasteurisation of fermentable extracts.
In the traditional method used in many breweries the liquid extract from the mashing process is boiled at about 103.degree. C. (218.degree. F.) after which the liquid extract is clarified, cooled and fermented after addition of brewers yeast. The fermentation occurs at about 13.degree. C. (55.degree. F.). Under these conditions an alcohol level of about 6% by volume is achieved by fermentation.
Brewing literature reveals that during and after the traditional process of boiling at about 103.degree. C. (218.degree. F.), the processes of coagulation and adsorption of nutrients on the coagulant are responsible for the removal from the germinated grain extract of many of the important nutrients required by yeast for fermentation and propagation.
With a view to preventing the loss of yeast nutrients resulting from the boiling process, a further known process has been developed which allows for the processing of the germinated grain at temperatures below 82.degree. C. (180.degree. F.) after which the liquid extract from the processed grain is cooled to about 13.degree. C. (55.degree. F.) and is fermented with brewer's yeast. Under these conditions where the liquid extract from the processed germinated grain is not boiled but is cooled directly to fermentation with brewer's yeast an alcohol content of about 9% by volume will result. This method is described in New Zealand patent specification no. 248338 248503/248973/250413/250975, and the processes described in that specification for preparing a soluble extract including yeast nutrients are as follows. Disclosed is a method of manufacturing an alcoholic beverage comprising the steps of:
(i) taking the soluble extract including yeast nutrients in a liquid form from processed moisture infused germinated grain where the processing temperature(s) (including any temperature of any of those temperatures used to activate the various germinated grain enzymes) is or are kept below 180.degree. F. to prevent said yeast nutrients being entrapped in coagulate such as that which would be produced were the processed moisture infused germinated grain to be boiled at atmospheric pressure; PA1 (ii) heating the said liquid extract to enhance enzyme activity therein but to a temperature below that where coagulates are formed which would cause yeast nutrient material to be entrapped in coagulate such as that which would be produced were the liquid extract to be boiled at atmospheric pressure; PA1 (iii) cooling the liquid extract of step (ii) to between about 50.degree. F. and about 60.degree. F. and fermenting the cooled liquid extract with oxygenated brewers yeast in the presence of an added fermented extract which has been prepared according to said steps (i), (ii), and (iii) so that the mixture begins fermenting with an alcohol content of about 3% by volume or higher and other products of fermentation to provide said alcoholic beverage. PA1 taking a fermentable soluble extract in liquid form from a brewers mash which has been processed according to any known method; PA1 mixing said fermentable soluble extract with a fermented fermentable extract which before fermentation was similar to the fermentable soluble extract, to produce a mixture; PA1 processing said mixture by heating said mixture to at least 51.degree. C. (124.degree. F.) in a heating zone, holding said mixture for at least 10 minutes in a holding zone and then cooling said mixture in a cooling zone to a fermenting temperature of between 10.degree. C. (50.degree. F.) and 15.degree. C. (59.degree. F.), all in a continuous flow; and PA1 fermenting said processed mixture with oxygenated brewers yeast to produce said alcoholic beverage. PA1 evaporating said fermentable soluble extract in liquid form within a vacuum vessel together with a spray dryer to evaporate the liquid to produce a fermentable soluble extract in powder form; PA1 dissolving said fermentable soluble extract in powder form with water to produce a dissolved powder product which constitutes the fermentable soluble extract for mixing with the fermented fermentable extract. PA1 taking a fermentable soluble extract in liquid form from a brewers mash which has been processed according to a method during which the temperature has been retained below 82.degree. C. (180.degree. F.); PA1 evaporating said fermentable soluble extract in liquid form within a vacuum vessel together with a spray dryer to evaporate the liquid to produce a fermentable soluble extract as a powder product; PA1 storing said powder product until required or transferring it to another location, and holding said powder product in a holding means adapted to provide a continuous controlled flow of said powder product; PA1 dissolving said continuous controlled flow of powder product with a continuous controlled flow of water in such proportions as to maintain a continuous flow of dissolved powder product at a selected specific gravity; PA1 mixing the continuous flow of dissolved powder product with a continuous flow of fermented fermentable extract taken from an outlet of a continuous fermenting plant in a volume ratio of substantially 1 to 1, to produce a mixture; PA1 processing said mixture by heating the mixture to between 51.degree. C. (124.degree. F.) and 60.degree. C. (140.degree. F.), according to the degree and type of infecting organisms in the mixture, holding the heated mixture in a holding zone for up to 20 minutes, then cooling the mixture to a yeast fermenting temperature of substantially 15.degree. C. (59.degree. F.) and returning it to an inlet of said continuous fermenting plant; and, PA1 fermenting said processed mixture, in accordance with known continuous fermenting methods, in a continuous fermenting plant to produce the alcoholic beverage.
The prior art, although extensive, does not disclose a method for achieving pasteurisation of fermentable extracts at temperatures below 71.degree. C. (160.degree. F.). Carrying out pasteurisation at temperatures below 71.degree. C. (160.degree. F.) would be advantageous in order to avoid the coagulation which occurs above 71.degree. C. (160.degree. F.) and which results in loss by adsorption of important nutrients required by yeast for fermentation.
It will be appreciated by persons skilled in the art that the term soluble extract, when taken from a brewer's mash, and as used in this specification, refers to an extract containing both fermentable material and yeast nutrients used in part for propagation.
It is therefore an object of the present invention to provide a method whereby pasteurisation of a fermentable extract from a germinated grain brewers mash can be achieved at temperatures below 71.degree. C. (160.degree. F.) and so avoid yeast nutrient loss.
Other objects of this invention will become apparent from the following description.